Luna 4 was the USSR's first successful spacecraft of their "second generation" Luna program. The spacecraft, rather than being sent on a straight trajectory toward the Moon, was placed first in an Earth orbit and then an automatic interplanetary station was rocketed in a curving path towards the Moon.

Luna 4, the second attempt of this program, achieved the desired trajectory but missed the Moon by 8336.2 km at 13:25 UT on April 5, 1963 and entered a barycentric 90,000 x 700,000 km Earth orbit. The intended mission of the probe is not known, it was speculated the probe was designed to land on the Moon with an instrument package based on the trajectory and on the later attempted landings of the Luna 5 and Luna 6 spacecraft and successful landing of Luna 9. (A lecture program entitled "Hitting the Moon" was scheduled to be broadcast on Radio Moscow at 7:45 p.m. the evening of April 5 but was cancelled.) The spacecraft transmitted at 183.6 MHz at least until April 6.

Lunar surface close-up photography

The purpose of this experiment was to obtain information on the characteristics of the lunar surface. These characteristics include the amount of cratering, structure and size of craters, the amount, distribution, and sizes of ejecta, mechanical properties of the surface such as bearing strength, cohesiveness, compaction, etc. Determination and recognition of processes operating to produce the lunar surface features also were among the objectives of this photographic experiment.

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